Cooling of combustor walls is typically achieved by directing cooling air through holes in the combustor wall to provide effusion and/or film cooling. These holes may be provided as effusion cooling holes formed directly through a sheet metal liner of the combustor walls. Opportunities for improvement are continuously sought, however, to provide improve cooling, better mixing of the cooling air, better fuel efficiency and improved performance, all while reducing costs.
Further, a new generation of very small turbofan gas turbine engines is emerging (i.e. a fan diameter of 20 inches or less, with about 2500 lbs. thrust or less), however known cooling designs have proved inadequate for cooling such relatively small combustors as larger combustor designs cannot simply be scaled-down, since many physical parameters do not scale linearly, or at all, with size (droplet size, drag coefficients, manufacturing tolerances, etc.).
Accordingly, there is a continuing need for improvements in gas turbine engine combustor design.